1. Field of the Invention
The present invention relates generally to a liquid crystal display (LCD) device. More particularly, the present invention relates to a thin film transistor (TFT) LCD device and a fabrication method thereof, in which a cross talk caused by an alteration of an electric field is prevented.
2. Description of the Prior Art
As widely known in the art, the TFT LCD device is a typical electronic display device functioning by deformation of liquid crystal molecules according to the electric field between confronting electrodes on lower and upper substrates. In the TFT LCD device, the upper substrate usually referred as a color filter substrate maintains a uniform voltage by mostly receiving signals from the lower substrate usually referred as an array substrate.
To provide such signals to the upper substrate, a so-called transfer is currently used for interconnection between the lower and upper substrates. The interconnection transfer is generally located between outer lead bonding pads of an LCD panel or at a peripheral region outside an active area, and also penetrates a liquid crystal layer.
However, this may cause a difference in voltage between central and peripheral regions in the entire panel. That is, a common signal is differently provided to each color filter region, so that undesirable cross talk is generated while degrading the quality of a screen of the LCD panel.
On the other hand, as another factor in good quality of the screen, the liquid crystal layer should have a uniform cell gap between the lower and upper substrates. One of conventional solutions to satisfy this requisite is to use a spacer ball 30 shown in FIG. 1. Referring to FIG. 1, the spacer ball 30 is interposed between the lower and upper substrates 10 and 20, thus uniformly maintaining the gap therebetween.
Such a conventional solution using the spacer ball has, however, some drawbacks. For example, since the spacer ball is only several microns in diameter, variations of diameter may often happen. In addition, due to the movement of grains in the spacer ball, a photoalignment layer may be destroyed or the grains may be agglomerated. Besides, the use of the spacer ball may cause the leakage of light. Unfortunately, these drawbacks may result in bad problems such as poor display and low contrast ratio. To solve these problems, various approaches such as the coloring of the spacer ball, the development of a fixed spacer, or the increase in hardness of the ball have been made, but satisfactory results have been not given.
Recently, one way has been proposed to overcome the drawbacks of the conventional spacer ball. The way is, as shown in FIG. 2, to form a supporting column 40 under the upper substrate 20. The supporting column 40 is made of photosensitive polyimide, photosensitive acrylic acid resin, photosensitive coloring resin, or photoresist by using a photolithography process. Generally, the supporting column has a trapezoid body shape and a round tip.
FIG. 3 illustrates a conventional LCD device employing a supporting column 32. As depicted in FIG. 3, a color filter layer 22 and a black matrix 23 are formed under a glass board 24 for the upper substrate. Next, indium tin oxide (ITO) layers 16 and 21 are formed respectively on a glass board 12 for the lower substrate and under the upper glass board 24. The supporting column 32 is then formed through the liquid crystal layer 26 by using the above-mentioned material and process. The supporting column 32 is placed at every pixel, and preferably disposed at a red or blue region.